The invention relates to dental materials based on polymerizable materials and containing a so-called tear-off material, i.e. a component which, after curing of the polymerizable component, can be removed (torn off) from the cured dental material with accompanying formation of a rough surface.
U.S. Pat. No. 5,839,900 discloses a process for preparing dental restorations in which pieces of fabric impregnated with the organic matrix material are laid onto a cast, shaped by pressing against the cast in a thermoforming process and subsequently cured. After the curing, the basic frame thus obtained is faced by applying a cover material. To ensure a secure adhesion between cover layer and basic frame, the latter is roughened before facing. Damage to the glass fibers embedded in the polymer matrix is often unavoidable, and in addition there is the risk that too much material is removed and unstable structures thus obtained.
DE 31 09 424 A1 discloses a process for manufacturing fiber-reinforced plastics items in which fibers impregnated with curable resins and covered with a flexible, expandable film on one or both sides, are laid onto a suitable mold, matched to this by vacuum-molding and then cured. The films either remain after polymerization on the cured plastic or are removed after curing. In both cases, items with a smooth surface are obtained.
The object of the present invention is the provision of dental materials which, after curing, have a surface which is suitable for direct further processing without additional roughening and cleaning.
This object is achieved by dental materials based on polymerizable substances and containing a component which is applied superficially to the polymerizable component and which can be removed (torn off) after the curing of the Polymerisable component with accompanying formation of a rough surface. The superficially applied component is also called tear-off material hereafter.
Mat-shaped materials which have a structured surface in particular are suitable as superficially applied component or tear-off material. Upon application to the uncured and thus still shapable polymerizable component, the structure of the tear-off material is transferred onto the polymerizable component and the latter is thus embossed with the tear-off material to a certain extent. Upon curing of the polymerizable component, the surface structure is frozen and is retained after the removal of the tear-off material.
Films or preferably fabrics can be used as tear-off material.
By films are meant mat-shaped materials which are characterized by a homogeneous polymer matrix and for example can be prepared by the extrusion of suitable filled or unfilled polymer materials.
Preferably, at least one surface of the films is structured, for example by embossing or perforating. Perforated films are preferred. The perforation allows the passage of polymerizable material which is removed together with the film, on tearing-off of the film, so that a particularly fine roughening of the surface is achieved.